The appendicular myology of Stegoceras validum (Ornithischia: Pachycephalosauridae) and implications for the head-butting hypothesis.

In this study, we use an exceptional skeleton of the pachycephalosaur Stegoceras validum (UALVP 2) to inform a comprehensive appendicular muscle reconstruction of the animal, with the goal of better understanding the functional morphology of the pachycephalosaur postcranial skeleton. We find that S. validum possessed a conservative forelimb musculature, particularly in comparison to early saurischian bipeds. By contrast, the pelvic and hind limb musculature are more derived, reflecting peculiarities of the underlying skeletal anatomy. The iliotibialis, ischiocaudalis, and caudofemoralis muscles have enlarged attachment sites and the caudofemoralis has greater leverage owing to the distal displacement of the fourth trochanter along the femur. These larger muscles, in combination with the wide pelvis and stout hind limbs, produced a stronger, more stable pelvic structure that would have proved advantageous during hypothesized intraspecific head-butting contests. The pelvis may have been further stabilized by enlarged sacroiliac ligaments, which stemmed from the unique medial iliac flange of the pachycephalosaurs. Although the pubis of UALVP 2 is not preserved, the pubes of other pachycephalosaurs are highly reduced. The puboischiofemoralis musculature was likely also reduced accordingly, and compensated for by the aforementioned improved pelvic musculature.

Total knee arthroplasty with the kinematic condylar prosthesis. A ten-year follow-up study.

Of 168 consecutive knees (118 patients) that had been treated with an arthroplasty with use of a kinematic total condylar prosthesis that allowed retention of the posterior cruciate ligament, 119 knees (eighty-four patients) were available for review at a mean of 10.0 +/- 0.7 years after the operation. The Hospital for Special Surgery knee score improved significantly, from a mean of 55 +/- 12 points preoperatively to a mean of 81 +/- 9 points at ten years (p < 0.0001). Radiolucent lines about the patellar component, present in thirty-five of eighty-three knees at the latest follow-up examination, were related to malpositioning of the tibial and femoral components. Six revisions were performed, and four of them were for a loose patellar component. The rate of deep infection was 1 per cent (one knee). Complications occurred in twenty-six knees (22 per cent). With revision as the end point, the rate of survival of the prostheses was estimated to be 96 per cent at ten years. The knee scores, the rate of survival of the implants, and the range of motion of the knees in the current study were similar to those reported previously for patients who had insertion of a total condylar prosthesis with sacrifice of the posterior cruciate ligament and for those who had substitution of the posterior cruciate ligament with a posterior stabilized prosthesis. A prosthesis that has a metal-backed tibial component and that allows preservation of the posterior cruciate ligament provides durable results, but loosening of the patellar component remains a major problem.

Total replacement for post-traumatic arthritis of the elbow.

Fifty-three of 55 consecutive elbow replacements for post-traumatic arthritis were followed for a minimum of two years (mean 6.3, range 2 to 14.4). The patients presented difficult management problems, having undergone an average of two previous operations per joint; 22 joints had suffered prior complications; 18 had less than 50 degrees of flexion and six were flail. One of three versions of the Coonrad prosthesis was employed in all. During the follow-up period, 10 patients underwent 14 revision procedures for aseptic loosening; 38 elbows are currently without progressive radiolucent lines. In two patients an elbow had to be resected, one for deep infection and the other for bone resorption following a foreign-body reaction to titanium. The current design of the Coonrad prosthesis offers a reliable option for the treatment of post-traumatic arthritis but should be used only in carefully selected patients over the age of 60 years.

Long-term results of various treatment options for infected total knee arthroplasty.

Of 73 infected total knee arthroplasties treated from 1973 through 1984, the outcome of various management options revealed that solid arthrodesis was obtained in 70%. Fifteen percent of those with a solid fusion had residual pain or even recurrence of infection. Aggressive debridement was successful in eight of ten (80%). Long-term follow-up results show reimplantations were successful in eight of 15 (53%) but were functionally successful in only five of 15 (33%). A treatment plan based on functional considerations follows. For acute infections a very aggressive initial debridement followed by primary closure over an antibiotic-soaked pack is carried out. The prosthesis is left in place if at all possible and if the bone-cement interface has not demonstrated loosening. The knee is debrided every two or three days until negative cultures are obtained. Antibiotic beads are then inserted, with reexploration at three weeks with new cultures. Parenteral antibiotics are given for a three-week period initially. If two successive surgical debridements fail to reveal a positive culture, the knee is closed and rehabilitation is begun. For chronic infections, the recommendations of Wilde and Ruth are followed, employing antibiotic-impregnated beads and spacers with staged debridements similar to the method described above. Finally, an accurate definition of the true value of any of these options is predicated on long-term follow-up studies, since options that seemed promising as an initial procedure have proved disappointing as more experienced and longer follow-up study is obtained.

Patellar tendon rupture after total knee arthroplasty.

Between 1973 and 1985, 18 knees in 17 patients were treated for rupture of the patellar tendon after total knee arthroplasty (TKA), accounting for 0.17% of the TKAs performed at the authors' institution during the same interval. Follow-up study was from two and one-half years to four years. Four ruptures occurred in patients who had had a distal patellar realignment procedure, and one occurred after knee manipulation. Only two xenograft reconstructions and two of four staple fixation procedures were successful. After treatment of the patellar tendon rupture, four knees developed deep infection. Avoidance of this complication seems paramount because the results of treatment are discouraging. Patients at high risk at the time of the initial TKA seem to be those with limited preoperative motion in whom surgical exposure is difficult.

Unicompartmental porous coated anatomic total knee arthroplasty.

Unicompartmental arthroplasty has been advocated for management of the older patient with unicompartmental arthritis. Implant breakage and loosening has led to modifications of implant design to metal backing and porous coating for potential bone ingrowth. A review of 28 cementless porous coated anatomic total knee arthroplasties two years after the operation revealed good to excellent results in 20 knees (71%). Six knees in five patients required revision for persistent pain. Only fibrous tissue ingrowth was observed. Five knees were considered potential failures based upon persistent pain and roentgenographic evidence of component loosening. This implant design is not acceptable with cementless fixation.

Results of revision total knee arthroplasties using condylar prostheses. A review of fifty knees.

Revisions of total knee arthroplasties for aseptic failure have provided varied results. In this review of fifty revisions in which a condylar prosthesis was used in carefully selected knees, the results were rated good or excellent in 76 per cent after an average length of follow-up of 4.8 years. At the follow-up examination, radiolucent lines were seen in 17 per cent of the knees. The complications included loosening of one or both prosthetic components in three knees (of which two were revised again); a hematoma in one knee; and a piece of loose cement, which had to be removed, in one knee. There were no deep infections. On the basis of these results, we concluded that revision total knee arthroplasty using a condylar prosthesis will have infrequent complications and will provide a satisfactory result in properly selected patients.

High tibial osteotomy.

The results of high tibial osteotomy performed in a 12-year period in 75 patients (88 knees) were followed for at least five years or until failure occurred. Of the 86 knees available for subjective follow-up evaluation, 64 were in men and 22 were in women. Roentgenographic data were available for 75 knees. The results were rated good (no or minimal pain, occasional analgesics required, slight limitation of activity), fair (regular analgesics required, noticeable decrease in activity), poor (moderate to severe pain, marked decrease in activity), or failed (arthroplasty required). On the basis of these definitions, 51% of the results were good, 9% were fair, 4% were poor, and 36% were failed. Results were satisfactory in 94% at two years, 87% at five years, and 69% at ten years. The absolute amount of angular correction did not correlate with the results. The change in axial alignment with time was unpredictable. Gender and age of patient were not factors in the outcome, although women seemed to require a longer period to become support-free. Better long-term results were obtained if the correction was to 10 degrees or more of anatomic valgus.

Pelvic mass causing vesical compression after total hip arthroplasty. Case report.

A 59-year-old woman developed a histiocytic response to methylmethacrylate debris in a loose total hip arthroplasty. This reaction eroded through the medial wall of the acetabulum, producing a pelvic mass and presenting with urinary symptoms. A combination of an abdominal approach for removal of the pelvic mass and a lateral approach for revision of the total hip arthroplasty was required. This condition should be considered in the differential diagnosis of a mass adjacent to a loose prosthesis.

Complications and mortality associated with bilateral or unilateral total knee arthroplasty.

The incidence of complications, the need for secondary surgical procedures, and the mortality rate associated with bilateral replacement of the knee performed simultaneously, performed during the same hospitalization, or performed during separate hospitalizations were compared with those after unilateral replacement of the knee. The incidence of complications after 290 simultaneous bilateral procedures was 9.3 per cent, which compares favorably both with the incidence of 7.0 per cent after 228 bilateral procedures that were done during the same hospitalization and incidence of the 12.0 per cent after 234 bilateral procedures that were performed during separate hospitalizations. The incidence for each of these groups compares favorably with the incidence of complications of 11.0 per cent after 501 unilateral procedures. The incidence of reoperation was 2.4, 4.8, 8.5, and 5.6 per cent, respectively, in the four groups, and the incidence of mortality was 5.5, 0.9, 3.8, and 7.0 per cent. None of these differences were statistically significant. These data indicate that the incidence of morbidity and mortality that is associated with simultaneous bilateral total knee arthroplasty is no greater than when the procedure is performed during the same hospitalization or separate hospitalizations.

Revision total elbow arthroplasty.

Over a ten-year period, thirty-three consecutive revision total elbow arthroplasties were performed at our institution. These were assessed at a minimum of three years after the revision, with an average length of follow-up of sixty-one months. Eighteen (55 per cent) of the elbows had a good result and fifteen (45 per cent) had a poor result. The poor results were due to infection in three elbows, loosening of the prosthesis in six, inadequate motion in two, continued pain in two, and prosthetic failure in two. Additional surgical revision with another implant was done in the fifteen elbows that initially had a poor result. Eventually the result was good in twenty-four elbows. The three elbows that became infected after surgical revision had a resection arthroplasty and all were rated as having a fair result. The data from this study indicated that reimplantation is a viable option for the revision of a failed total elbow arthroplasty, although more than one revision may be required. They also suggested that young patients who have post-traumatic arthritis should not undergo a total joint replacement, and that revision procedures should be performed in settings that can offer several surgical options and by surgeons who have had experience with these options. Alternatives to reimplantation as a revision procedure should be considered in selected patients.

Failed total knee arthroplasty treated by arthrodesis of the knee using the Ace-Fischer apparatus.

Twenty-eight patients were treated for a failed total knee arthroplasty by arthrodesis with a new type of biplane external fixator. The reasons for failure of the total knee arthroplasty were sepsis in twenty-five patients, loosening in one, pain of unknown etiology in one, and fibrous ankylosis in one. The mean duration of fixation with pins was 112 days. In twenty knees, arthrodesis occurred without further treatment. One knee fused after the application of dual plates, and one united after treatment with electrical stimulation. Of the remaining six patients, one had an above-the-knee amputation for persistent non-union and five had a persistent pseudarthrosis. The extent of loss of bone appeared to be the most important factor influencing union of the primary arthrodesis. One patient who had a solid union of the arthrodesis had a persistent non-union after a fracture at the site of a femoral pin. The rate of success of 68 per cent that was achieved with the device that we used is similar to the rates obtained with the use of older external fixators.

Management of infected total knee arthroplasty.

A retrospective study of the Mayo Clinic experience with the management of 61 infected total knee arthroplasties treated between 1970 and 1980 revealed rheumatoid arthritis as an underlying diagnosis in 47%. Previous operations had been performed in 58%. Arthrodesis was the most frequently utilized salvage technique and was successful in 83%. Reimplantation of a new prosthesis was successful in 63%. Debridement alone was successful in six knees when performed early for acute infections.

The outcome of failed knee arthrodesis following total knee arthroplasty.

After failure of total knee arthroplasty, arthrodesis was attempted in 120 cases, and unsuccessful in 25 (21%). Failure of arthrodesis was defined as nonunion persisting one year after arthrodesis or reoperation to obtain union. The number of attempts at arthrodesis ranged from one to four. The most frequent reasons for reoperation were persistent pain and instability. Most failures were caused by poor apposition owing to bone loss. Union was obtained in ten knees (average follow-up period, 44.5 months), but not in 11 (average, 35.3 months).

Revision total knee arthroplasty.

Careful attention to axial alignment, soft tissue balance, and stability will minimize prosthetic failure. In revision arthroplasty a prosthesis designed to replace bone loss with the least constraint possible should be used. In the current series revision of the noninfected failed total knee arthroplasty has provided satisfactory results in 50% to 60% of the patients. We believe that use of the newer implants and instrumentation will improve results markedly.

A previously unreported cause of pain after total knee arthroplasty.

Total knee arthroplasty achieves consistently excellent results in most patients. The most common causes of failure are loosening and infection. This article reviews the records of five patients in whom intraarticular fibrous tissue hypertrophy was the cause of pain after total knee arthroplasty. All of the patients had increasing pain and decreasing knee motion. Evaluation for loosening, malalignment, intraarticular debris, and infection gave negative results. Examination revealed a blocked range of motion and a palpable, tender, intraarticular mass. Injection of anesthetic relieved the symptoms. Surgical excision of the hypertrophic fibrous tissue relieved symptoms and increased knee range of motion. This cause of pain in the total knee arthroplasty patient is rare.

Early motion with cast-brace after modified Coventry high tibial osteotomy.

The records of 31 patients who were treated by a modified Coventry high tibial osteotomy were reviewed, and the early results of postoperative management with a cylinder cast were compared with those with early motion in a cast-brace. Thirteen patients (15 knees) who had immobilization in a cylinder cast after surgery for an average of 44.3 days had lost a mean of 10 degrees of flexion at three months of follow-up study. Their average total hospitalization was 15.5 days. Eighteen patients (19 knees) treated by early motion in a cast-brace had not lost any preoperative flexion at three months of follow-up study. The two most recent of these patients received continuous passive motion in the immediate postoperative period. The average total hospitalization for this group was 10.7 days. One patient in the cast-brace group had a significant loss of correction at the osteotomy site during healing. Eleven of the patients treated by a cylinder cast (84.6%) and 17 of the patients managed with a cast-brace (94.4%) stated that they had been improved by the surgery at this early stage. There were no nonunions or loss of internal fixation in either of the two groups. Early motion in a cast-brace (with a continuous passive motion machine, if available) is safe and is comfortable for and well accepted by patients.

Polycentric total knee arthroplasty. A ten-year follow-up study.

After review of the first 209 polycentric total knee arthroplasties (in 159 patients) performed at the Mayo Clinic between July 1970 and November 1971, we found that the calculated probability of the arthroplasty remaining successful ten years postoperatively was 66 per cent. Actual results showed 42 per cent of the arthroplasties to be successful in patients who were still alive at review; another 24 per cent were successful but were in patients who had died or were lost to follow-up before ten years postoperatively. In 34 per cent failure occurred, which we defined as reoperation for any reason, unacceptable pain, or loss of function. The most common causes of failure were instability or ligament laxity (13 per cent), loosening of a component (7 per cent), infection (3 per cent), and patellofemoral joint pain (4 per cent). Prior knee surgery significantly decreased the probability of success, as did axial malalignment of the prosthetic components at operation.

Management of the infected total joint arthroplasty.

Infection is the most severe complication of total joint arthroplasty. Prompt recognition and correct management, as well as prophylaxis against infection, are essential to minimize morbidity and maximize function. In this article, the etiology and diagnosis of prosthetic infection and the management of infected total arthroplasties of the hip, knee, ankle, shoulder, elbow, and wrist are discussed.

Surgical treatment of ligamentous instability after total knee arthroplasty.

During the period of January 1, 1972 through October 31, 1982 seven knees in seven patients had ligamentous reconstructions for instability following total knee arthroplasty. The type of ligamentous instability included severe medial instability in six and a combined severe medial and mild lateral instability in one patient. The surgical technique utilized to reconstruct the ligaments included proximal and distal advancement of the medial collateral ligament. In five of the seven, additional soft tissue surgery was combined with tightening of the medial collateral ligament. Unfortunately, ligamentous reconstruction failed to restore stability to the knee in any of the seven patients. Four patients required revision total knee arthroplasty. Instability of the knee necessitated full-time support with a brace and the seventh patient manages his instability without a brace. Ligamentous reconstruction without component revision is inappropriate in the treatment of the unstable knee following total knee arthroplasty.