Table of Contents
updated 10/8/2023 tpg
Are you considering resurfacing or total hip replacement (THR) as a solution for your hip issues? In recent years, there has been a growing interest in resurfacing and hip replacement procedures as solutions for hip-related conditions and disorders. However, various myths and misconceptions have emerged along with the advancement of these treatments.
In this article, we hope to provide a clearer understanding of these procedures and help you make informed decisions about your hip health. We will explore the truth behind concerns about metal ions, recovery capabilities, suitable candidates, implant longevity, and more.
"Those metal ions are going to poison you."
All artificial implants release wear and corrosion particles into your body. 70 years of joint replacement history tells us that our bodies can tolerate these fairly well. There is probably individual variability in our body’s response to these foreign particles, but this is poorly understood. At this point, there is no test that has been validated to predict any individual response to foreign particles. There are several issues that I will discuss as it relates to foreign material.
- Metal allergy
- Cobalt toxicity
- Cobalt carcinogenicity
Metal allergy appears to be a myth. There is no convincing scientific evidence that our bodies are allergic to implanted metal. It is well documented that skin sensitivity to metal does exist. The most common skin sensitivity is to Nickel. Skin patch tests to nickel show a positive result in 20% of the population. But that 20% do not have a higher failure rate with implants containing small amounts of nickel (stainless steel, cobalt-chrome).
The blood Lymphocyte Transformation Test (LTT) has been touted by many to determine if a person is allergic to metals. Your blood is drawn and sent to a lab where the reactivity of your lymphocytes is tested for various metals. We have found that 58% of people tested as “allergic” to at least one metal on the panel. The most common was nickel at 39% (present in cobalt-chrome alloy). Titanium “allergy” was seen at 19%. This would mean that at least 40% of people are allergic to their knee replacement or hip resurfacing and at least 20% to their hip replacement. In our study, a positive LTT preoperatively did not predict any negative outcome with hip resurfacing. Therefore, we would have to conclude that the LTT has no predictive value…it does not do what the lab says it does. In fact, a $500 lab test is being sold without any data that actually validates it. There is no value in getting metal allergy tests.
Cobalt toxicity is a real but rare problem. There was a health crisis in Canada when cobalt sulfate was added to beer years ago. Cardiac failure occurred in some patients, but unfortunately, blood levels of cobalt were not reported. From other rare case reports of failed THR, it appears that a cobalt level well above 100 ug/l (perhaps over 500ug/L) is required to cause cardiac toxicity. Cobalt and chromium are both naturally occurring in our bodies, but very high doses can be problematic. A normal blood level for patients without implants in most labs is less than 1.5ug/L. 80% of my patients fall in this range even with a metal-metal bearing. The mean level for my hip resurfacing patients is 1.4ug/L. Metal-plastic THR mean levels are 0.5ug/L, while Total Knee Replacement (TKR) mean levels are 3.3ug/L. If you are one of the nearly 1 million patients having a TKR in the US annually, you are more likely to have an elevated cobalt level than if you have a hip resurfacing!
There is some evidence that levels above 20ug/L may cause mild systemic toxicity in some patients. This includes neuropathy, tinnitus, and hearing loss, NOT cardiac failure. Unfortunately, these “mild” toxicity symptoms are very common for other reasons in aging people, therefore it is never clear if they are related to the cobalt level itself in any individual case. The best evidence indicates that these types of symptoms are most likely not caused by the blood ion level unless the level is over 20ug/L. I have used chelation with N-acetyl cysteine (NAC) rarely in patients with levels above 20ug/L without symptoms if the hip itself is functioning well. With a level above 20ug/L and systemic symptoms, I believe it is best to remove the implant even though you are not sure whether the symptoms are related to the cobalt level. Although I have revised patients with metallosis (who have a mean Cobalt level of 70ug/L), I have not yet revised anyone for isolated elevated ions.
Metal ions released from implants do not cause cancer. This concern arose from basic science studies where DNA changes were seen in cells in tissue culture when exposed to cobalt at sufficient concentrations. Several long-term clinical studies have found no difference in cancer rates in patients with metal-metal bearings, metal-plastic bearings, and those in the general population without implants. The studies in Finland by Visuri are the best. Also, more recent studies of the British and Australian registries indicate a lower 10-year all-cause mortality in hip resurfacing compared to THR.
The most significant problem with metal debris is a local inflammatory reaction to either wear or corrosion debris around the hip joint. Think of having dust blown into your eye. This causes severe inflammation, which is driven by the immune system, but it is not an allergic response to dust. All people’s eyes will become irritated to some degree. In the same fashion excess wear or corrosion debris can cause irritation of your hip.
In controlled laboratory wear testing, the metal-on-metal bearing of hip resurfacing releases the least amount of wear debris of any implant except for ceramic-on-ceramic THR bearings. A well-positioned implant will never fail due to the accumulation of excess wear debris (metallosis, or Adverse Wear Related Failure [AWRF]). However, if the socket component is placed too steeply (high inclination) or too tilted forward (high anteversion) an abnormal wear pattern termed “edge loading” can rarely occur leading to metallosis (5% of sockets outside the established safe zone). Irritation from excess metal wear debris results in a large fluid collection with thick white fluid resembling pus (but no bacteria are present). The wall of the fluid collection is very thick and permeated with grey metallic debris. There is almost never any damage to muscles or other vital structures. The correct treatment is the removal of the fluid and careful excision of most of the cyst wall with the metal debris. And of course, correction of the faulty cup position or change to a different bearing type. Reports of damage to muscles or vital structures from AWRF in failed hip resurfacing cases are usually due to overly aggressive surgery. Those who believe in the allergy myth want to remove every bit of tissue and then the overly aggressive revision operation causes more harm.
A well-positioned hip resurfacing cup puts off less wear debris than most THR components in use today. However, if the cup is malpositioned, a small percentage (5%) will begin to edge-load and produce large amounts of wear debris causing a failure due to wear debris overload (AWRF). I began to understand this problem in 2007; by 2009 we developed a safe zone (RAIL) for placing the components as well as intra-operative x-ray techniques to ensure the correct placement of the cup within the RAIL guidelines (Relative Acetabular Inclination Limit). Since 2009 (>5000 cases), not a single cup has failed to meet the RAIL guidelines, and no wear failures have occurred. Problem solved.
But THR continues to have a major problem with trunion corrosion accounting for a 0.1-5% rate of failure by 10 years. Furthermore, in my experience, trunion corrosion results in much more severe soft tissue inflammation than occurs in a hip resurfacing bearing wear failure (metallosis). The THR problem with wear was solved with the introduction of crosslinked polyethylene 20 years ago. But the problem of trunion corrosion has now become a major source of concern. We do not fully understand this problem, nor do we yet have a solution for this problem.
The trunion is the connector between the head and the stem (hip resurfacing does not have this junction). Corrosion at this connector releases metal ions at a low rate but also something else that is very irritating to the tissues. The metal blood levels are typically mildly elevated. Severe inflammation and even extensive muscle damage can be seen. But similar metal levels are seen in many well-functioning hip resurfacing patients without any tissue reaction. Therefore, I know that the cobalt and chromium particles coming off the THR trunion in cases of trunion corrosion is NOT the source of the tissue reaction. Many THR surgeons think it is because they are unaware that well-functioning hip resurfacing patients often (20%) have mildly elevated levels.
With hip resurfacing, I have had a rate of wear failure of 0/5000 since 2009, with THR the rate of trunion corrosion failure is 0.1-5% (5-250/5000) by 10 years. And THR surgeons claim that metal wear failure is the reason NOT to have a hip resurfacing? Instead, the risk of trunion corrosion is another reason not to have a THR.
"Total hips are now so improved that they will last 30 years."
Actually, in young patients (<50) implant survivorship is approximately 83% at 10 years and 50% at 20 years. Based on this ….it is hard to say: “your implant will last 30 years”. Most clinical data is derived from older folks (mean age 70), where implant survivorship is 95% at 10 years and the patients are unlikely to live 30 years.
If you have a series of patients who are mostly old and have a few younger ones sprinkled in, it is inaccurate to assume that the overall results apply equally to the younger subset. The only exception is ceramic-ceramic THR where a few expert surgeons have shown similar implant survivorship to HRA. But this does not apply to ceramic-polyethylene implants. Extrapolating results achieved in older patients to younger patients is inaccurate.
Extrapolating benchtop laboratory wear testing to clinical durability predictions is likewise inaccurate. It is true that idealized testing of wear in the laboratory would predict extremely long lifespans for ceramic on vitamin E crosslinked polyethylene bearings.
But in real life, it is impossible to achieve “ideal” implant positions. Also, wear testing machines don’t accurately mimic complex patient motions and loading. Furthermore, idealized testing cannot predict breakage due to edge loading and other activity-related factors. Finally, there are far more failure mechanisms than just wear which are not accounted for. Clinical studies account for all failure modes.
The only valid data is actual clinical data in younger patients. Few surgeons have it, and the registries show fairly poor “average surgeon” outcomes. It is fair to say that giving a 30-year lifetime estimate for THR is engaging in wishful thinking.
"Total hips allow the same function as hip resurfacing."
No artificial joint makes the hip completely normal. Patients that have worn through their cartilage surface usually find an artificial joint to be an improvement. Some even say they are normal again.
A hip resurfacing mimics the natural hip joint more closely. The load is passed from the femoral component in a more natural fashion to the top of the head, rather than through the THR stem to the femoral shaft (thigh bone). Loading the thigh with a THR stem feels unnatural to most people and results in limitations.
At least 11 scientific studies demonstrate the superior function of hip resurfacing. Many studies show no difference. None show the superiority of THR. The studies that show equivalence just place the bar too low. If I place the bar only one foot off the ground, any patient can hop over, and we can erroneously conclude that there is no difference. The three best studies showing hip resurfacing superiority are as follows.
- Pritchett reported on 332 patients in which he had performed a THR on one hip and a hip resurfacing on the other. 86% preferred the resurfaced hip, and only 6% preferred the THR.
- Barrack evaluated several hundred matched young patients with THR and hip resurfacing with detailed activity questionnaires that took the bar way above standard hip questionnaires typically used in THR research. “When controlled for age, sex, and premorbid activity level, patients with hip resurfacing had a higher incidence of complete absence of any limp, lower incidence of thigh pain, lower incidence of perception of limb length discrepancy, greater ability to walk continuously for more than 60 minutes, higher percentage of patients who ran after surgery, greater distance run, and higher percentage of patients who returned to their most favored recreational activity.”
- Cobb has done numerous gait studies demonstrating that THR and hip resurfacing patients walk equally well at slow speeds, but the gait at fast walking speeds is more normal in hip resurfacing patients.
Two anecdotes that illustrate these findings are the stories of Bo Jackson who had a THR and struggled to perform as a designated hitter in baseball and has already had to revision operations for implant failure in 23 years. This is exactly what the data in young people would predict. On the other hand, Andy Murray returned to win the European Open men’s singles tennis event 1 year after hip resurfacing and is currently ranked i# 37 in men’s tennis 4 years out from his metal-on-metal hip resurfacing.
There are two biomechanical reasons why hip resurfacing is more functional. Normal hip bearing size provides near-normal stability. Load transfer to the top of the head is more normal than loading the thigh through a THR stem. We will discuss stability later.
The THR stem is the main reason why patients struggle to perform after THR. In typical less-active patients who have THR, approximately 30% report slight or mild thigh pain. 3-5% report moderate to severe thigh pain. This is caused by load transfer from the stem. This is just with activities of daily living. When patients with THR try to return to impact sports (see Barrack above) they are unable. Many patients have pain due to the abnormal load transfer of the stem to the thigh bone (femur), with impact the sensation is naturally more pronounced and THR patients are often unable to overcome this discomfort. On the other hand, about 40% of my hip resurfacing patients choose to participate in impact sports, the only limitation is occasionally in distance runners. In some patients running more than 2-3 miles is limited, but many who have the desire are even able to run triathlons, marathons, and even ultras.
If you want to walk normally at fast speeds or if you want to run or play impact sports, you want a hip resurfacing.
"Anterior total hip replacement has the fastest recovery."
There is no difference in recovery between the anterior and posterior approaches in THR. Neither is there any between hip resurfacing and THR. But there is a better final recovery with hip resurfacing. As discussed in the previous section, hip resurfacing patients regain more normal hip function.
My recovery protocol for both operations depends on the patient’s bone strength. All reasonably healthy people can have surgery as an outpatient at our surgery center. They go home or to a hotel within several hours after their surgery. They walk in the surgery center with crutches and learn to climb stairs. Costly hospitals filled with resistant bacteria and sick patients can be avoided altogether.
Narcotic medications are usually only needed for 3-4 days. Once patients are off these, they may resume driving and resume some remote work. Most people return to desk work in an office within 1-2 weeks. They may also resume upper body exercises including weightlifting. The only therapy required is a progressive walking program. Crutches for 1-2 weeks, cane for 1-2 weeks. Walking 1 mile without an assistive device in 6 weeks. Stairs are one leg at a time for 4 weeks, foot-over foot with the rail at 4-6 weeks. Most people still have a slight limp at 6 weeks, but none at 3 months. They no longer need a rail at 3 months. Walking more than a mile, swimming, golf exercise bike, elliptical, and light leg weightlifting is OK after 6 weeks. These light aerobic activities are continued until 6 months at which time full unrestricted activities are allowed including impact sports and heavy lifting.
Range of motion (ROM) is restricted past 90 degrees for 6 weeks. Full ROM is allowed after 6 months including kayaking, yoga, gymnastics, and ballet.
At 1 year, extreme activities such as contact sports, slide tackling in soccer, and rock climbing are approved.
People with weak bones require more restrictions in the first 6 months to prevent fracture but are also back to full activity by 6 months.
Many of the restrictions are required to allow adequate healing of the muscles and bone. The bone is weakened by surgery and returns to baseline by 6 months. Bone ingrowth into the implant is 90% complete by 6 months. The ligaments and muscles cut are also fairly well-healed by 6 months.
Most patients are better than pre-op by 6 weeks, 90% healed by 6 months, 95% healed by 1 year, and as good as they are going to get by 2 years.
In most patients near normal strength and ROM is achieved. Unless they have another limiting condition or are deconditioned, virtually all patients can return to their premorbid (before the hip arthritis became limiting) activity or sports activity including running 1-3 miles. Many, but not all patients desiring to return to distance running are able to do so. But some are limited to 1-3 miles due to residual discomfort with running.
I encourage full and unrestricted activity because, unlike THR, hip resurfacing does not fail with extreme use. The advantage of an anterior approach for THR is a faster operation and lower dislocation risk than posterior THR (but still higher than hip resurfacing). The disadvantage is a higher femoral fracture and infection rate. There is no difference in the recovery rate. Also, the function is no different for an anterior vs posterior THR, but THR has a lower final functional outcome than hip resurfacing.
The remaining question is whether hip resurfacing done through an anterior approach would lead to better ultimate function than one done through a posterior approach. This is not known. The only abnormal muscles we see after healing with a posterior approach are the 4 short external rotators (piriformis, obturator internus and externus and quadratus femoris). I detach these 4 muscles from the bone and repair them back to bone at the end of the operation. Nevertheless, they do not usually heal and function completely normally. But they are minor muscles in the hip and most people function at a very high level even though these are abnormal.
I do recommend exercises for these muscles after they have fully healed in 6 months. The other major muscles around the hip return to completely normal (as evidenced by anecdotal MRI comparison of both hips 1-year postop). Theoretically, an anterior approach avoids the rotators. But this is not exactly true either, because if you observe an anterior hip approach, the "tissue" at the posterior edge of the greater trochanter is released to allow the femur to be pulled out of the wound. This "tissue" is the rotator. They are not dissected off as completely as in a posterior approach, but they also are not repaired. Which is better? Nobody knows. It seems to be more difficult to perform a hip resurfacing through an anterior approach.
Many years ago an excellent surgeon I know reported a 9% intraoperative femoral neck fracture rate, and subsequently gave up resurfacing. There is now one recent publication of mid-term outcomes with anterior hip resurfacing and the implant survivorship is 93% @ 10 years. My implant survivorship currently is 99% @ 17 years. Clearly, at this point, durability is greater when done posteriorly. My suggested explanation is that the operation is so much more difficult from the front, that the surgeon has a much tougher time getting it right. But this is durability data.
What about function? How would we document the superior function of an anterior approach? Gait studies show normal fast gait with posterior resurfacing, so gait studies would be unhelpful. Maybe we could take a matched cohort of distance runners and see if one group is more likely to return to distance running after 1 year. Because the failure rate is so much lower with the posterior approach, and there is no clear evidence on function, I will stick with the posterior approach.
"Women are not good candidates for hip resurfacing."
Women are excellent candidates and have the same outcome as men. Most hip resurfacing surgeons and Smith-Nephew Richards (SNR - manufacturer of the dominant BHR implant) discriminate against women because past data showed that hip resurfacing durability was less in women. In various studies, women had higher failure rates due to fracture, metallosis, and cup loosening. Femoral loosening was also a problem seen in older women with weak bones.
In my earliest cases, I had a higher failure rate in women compared to men due to metallosis and cup loosening. One of the major contributing causes was that young women desiring hip resurfacing had a much higher rate of dysplasia diagnosis than young men or older patients. It is well known that dysplasia also carries a worse outcome with THR.
Although younger women had more failures with hip resurfacing than men, they still had fewer failures than if they had a THR instead. Therefore, the common recommendation to avoid women in hip resurfacing made no sense to me. Additionally, hip resurfacing allows better functional outcomes than THR. Therefore, a woman should be allowed to choose between hip resurfacing and a THR even if the hip resurfacing had a higher failure rate. Durability and function are two separate factors that a patient has a right to consider.
I never agreed with most other hip resurfacing surgeons on this issue and continued to offer hip resurfacing to women. I was able to do so because the Zimmer Biomet Magnum/Recap implant that I use has remained available in all sizes, while SNR withdrew the smaller sizes required for women and also placed a warning on the label which made it legally hazardous for surgeons to implant women even if they happened to have a larger joint. Meanwhile, I worked to modify the hip resurfacing procedure to lower the failure rate in women.
In the last 10 years, my outcomes have improved substantially from 89% to 99% overall 10-year implant survivorship. The results in men improved, but they improved even more in women; this finally closed the gap 10 years ago. This means, for the last 10 years, I have achieved better durability with hip resurfacing than all THR types for both men and women equally.
Women can have a highly functional, stable hip resurfacing, with the same low failure risk as men.
"Patients with camFAI are not good candidates for hip resurfacing."
Men with cam Femoral Acetabular Impingement (camFAI) are in fact classically the best candidates for hip resurfacing. Most (80%) of the young men that I perform hip resurfacing on have this mild femoral deformity which likely contributed to them getting severe arthritis at a young age (40-60).
This deformity is manifested as a femoral head that is not centered on the neck. The head is like a ball of ice cream sliding off the cone posteriorly and inferiorly. In addition, there is often an additional bump of bone at the anterior/superior head/neck junction. There is considerable variability in the degree of this malformation. Lack of an anterior offset between the head and neck leads to a cam effect when the hip is flexed and internally rotated.
Cam FAI probably develops as a growth plate slip in the late teenage years. The male growth plate closes at age 12-14 years. It is a painless condition until the repetitive cam effect damages the labrum and hyaline cartilage of the hip, usually in the anterior-superior corner of the joint. Patients who present early can be treated arthroscopically. But most patients don’t present until substantial cartilage is lost (severe osteoarthritis).
At this point, hip resurfacing is the best treatment. The lost cartilage surface is restored with metal surfaces; the deformity is corrected by differentially resecting the femoral head bone more from the inferior and posterior side and moving the head center more anterior and superior. The bump is also removed. The result is improved anterior offset as well as new artificial cartilage. This same condition is seen less commonly in women. 17-year implant survivorship is 99%.
"Uncemented femoral components don’t work in osteonecrosis."
Completely uncemented hip resurfacing has the highest success rate in the published literature for osteonecrosis at 99% 15-year implant survivorship.
Osteonecrosis is chiefly a disease of young men. The most common cause is high alcohol consumption. It can also be caused by high doses of corticosteroids (not testosterone) or major trauma such as a fracture or dislocation (not a slip and fall). The blood flow to the head is decreased and a section of the head dies and collapses. This results in severe pain.
Hip resurfacing with a cemented femoral head is somewhat more durable than THR, but completely uncemented HRA has the best outcomes. My 10-year implant survivorship improved from 85% to 99% after adopting the uncemented femoral component.
Many hip resurfacing surgeons remain skeptical because they think bone in growth does not work in a head that is dead. This is true, but neither does cement. Obviously, the head is still alive if we can anchor an implant to it for over 10 years. The problem with osteonecrosis is that there is a large dead segment which creates a bone defect under the implant.
The remaining bone is very much alive and even bleeds vigorously. It still seems to be trying to heal the dead collapsed portion. Filling the defect with cement can cause more surrounding bone death and lead to failure. Cement cures in an exothermic reaction, a big bolus of cement in a big defect can cook the surrounding live bone. The same can occur in cases of osteoarthritis with large cysts (holes in the bone).
With the uncemented implant, I can always achieve a good initial press-fit on the remaining live bone. I graft the defect with bone shavings harvested from the socket preparation. The hypervascular remaining live bone readily grows into the uncemented component. That’s why my implant survivorship has improved so much. Because it works so well, I can now take on ever more severe cases with up to 50% of the head missing due to necrosis.
"Ceramic-on-ceramic resurfacing is the answer."
Ceramic-on-ceramic hip resurfacing will have a difficult time outperforming the current gold standard, uncemented metal-on-metal hip resurfacing which has a 99% 15-year implant survivorship. There are not yet any published data on the trials with ceramic-ceramic.
The main reason to pursue these new bearings is to take advantage of their superior wear characteristics. Ceramic-on-ceramic have the lowest benchtop laboratory wear rates, they are the only bearing better than metal-on-metal, the current gold standard. But metal-on-metal already has such a low wear rate that it can never wear out in anyone’s lifetime.
But metal-on-metal has an Achilles heel. If the socket is malpositioned in too steep or anteverted a position, a small percentage (5% of these) will suffer edge-loading mechanics and start releasing large amounts of metal debris. How often does this happen? I have published several papers on this topic. The first showed a 1% 10-year failure due to metallosis before the time we were aware of proper cup positioning. The second paper outlines a safe zone for socket positioning (RAIL: relative acetabular inclination limit) to avoid metallosis. In the third paper, we validate the safe zone. We evaluate a subsequent cohort of patients where we were able to place 100% of cups within the safe zone and experienced no cases with excessive ion levels or metallosis. I have not had a single case of metallosis in over 5000 cases since 2009.
The problem with metallosis has been solved in metal-on-metal bearings. The only remaining problem is one of perception and misinformation. The diagnosis of a metallosis failure is very straightforward. But many surgeons who do not perform hip resurfacing are quick to diagnose this problem without meeting the diagnostic criteria. The problem comes when a patient has residual unexplained pain. In a THR, where this occurs in 20% of cases, nobody suggests metal allergy as a cause, in hip resurfacing, where this occurs much less commonly, a presumptive diagnosis of metal allergy or excess ions is frequently made by uninformed surgeons evaluating an unhappy patient with hip resurfacing. A small residual fluid collection is seen in 30% of well-functioning THR and hip resurfacing cases. This is a normal postoperative finding. In a painful THR this may be misdiagnosed as a trunion failure, in a hip resurfacing it could erroneously be called a metallosis case.
Revision for unexplained pain carries a very low success rate. Far less than 50% of patients are satisfied. After all, if you don’t understand the problem, you can’t really expect to fix it, but sometimes you get lucky. I sometimes offer my own patients with unexplained pain a revision with this proviso, but I do not recommend it. I do not offer this option to others.
If we had a ceramic-on-ceramic hip resurfacing that otherwise worked as well as the current gold standard metal-on-metal variety, this problem with misdiagnosing unexplained pain would go away. It would be great to rid ourselves of this thorny problem.
But ceramic-on-ceramic may not be as good for several reasons. First, the early fracture/head collapse rate may be higher due to a smaller supporting stem. Second thin shells of ceramic (4mm) may fracture with repetitive high impact. Third, squeaking may be a problem. Finally, the porous titanium coating may detach from the ceramic cup after many years. I have published my experience with this problem with the Corin metal-on-metal system which had titanium coating that debonded from a cobalt substrate between 8-10 years postop. On the other hand, the ZB Magnum cup with the same type of coating that I have used for the last 17 years has not had that problem. Will titanium remain adhered to a ceramic shell over the long run in highly active patients? This is my main concern.
Having said this, I would welcome the opportunity to offer patients this option if they desired. I personally would have a metal-on-metal. Ceramic-on-ceramic is unlikely to beat 99% of 17-year KM implant survivorship in over 5000 cases.
"Uncemented resurfacing is better."
Not a myth! My data demonstrate that it is better. In my study , the excess failure rate due to loosening of the cement is 1% at 10 years. That does not seem like much. But if I used cement, my failure rate would double. My failure rate due to any cause is currently <1% by 15 years.
All hip resurfacings have an uncemented (porous, bone ingrowth) socket. Most have a cemented femoral component. The Recap/Magnum metal-metal implant that I use, and Jim Pritchett’s metal-poly implant are both completely porous.
Cement offers immediate fixation but kills some bone in the curing process. Late failure can occur due to cement fatigue. Porous fixation requires an initial tight press fit and time for ingrowth. Failure of ingrowth has never occurred in >5000 of my cases. Once ingrown, a porous coating is more durable than cement.
I could find no evidence that early femoral failure due to fracture or head collapse was affected by the choice of fixation (cement vs uncemented). However, by ten years the rate of femoral loosening was 0.9% vs 0.04%.
Cement actually works much better than I predicted 20 years ago. The cement in a femoral resurfacing is generally loaded in compression which is favorable for cement. Cement fixation in resurfacing has therefore done much better than cement in total hips and total knees.
Cement seems to work especially well if the femoral head bone is hard and there are no large defects. If the bone defects are cavitary and can be filled with bone graft and cemented over, the outcome is better than if the defect is filled with exothermic cement. In osteonecrosis, the defects tend to be segmental which makes it hard to use this grafting technique, so the outcome is worse. In osteoporotic bone, the cement also penetrates more deeply into the bone and burns more bone causing more failures. That is why McMinn has more failures in older women. Cement works best in hard bone and with contained defects that are grafted.
Porous fixation is technically easier, works in all cases, can be used in cases with extensive bone loss, and carries the theoretical advantage for long-term fixation well beyond 10 years.
Currently, my 15-year implant survivorship is 99% with fully porous Zimmer Biomet Recap/Magnum metal-metal Hip resurfacing in over 5000 cases. I do not exclude people based on age, sex, diagnosis, or implant size. I resurface heads with up to 50% bone loss in younger patients. No one can match these results – with the BHR or any other device.
1. Gaillard-Campbell, D.M. and T.P. Gross, Femoral Fixation Methods in Hip Resurfacing Arthroplasty: An 11-Year Retrospective Comparison of 4013 Cases. J Arthroplasty, 2019. 34(10): p. 2398-2405.