Richard H. Walker

The Effect of the Orientation of the Acetabular and Femoral Components on the Range of Motion of the Hip at Different Head-Neck Ratios*

Background: Prosthetic impingement due to poor positioning can limit the range of motion of the hip after total hip arthroplasty. In this study, a computer model was used to determine the effects of the positions of the acetabular and femoral components and of varying head-neck ratios on impingement and range of motion. Methods: A three-dimensional generic hip prosthesis with a hemispherical cup, a neck diameter of 12.25 millimeters, and a head size ranging from twenty-two to thirty-two millimeters was simulated on a computer. The maximum range of motion of the hip was measured, before the neck impinged on the liner of the cup, for acetabular abduction angles ranging from 35 to 55 degrees and acetabular and femoral anteversion ranging from 0 to 30 degrees. Stability of the hip was estimated as the maximum possible flexion coupled with 10 degrees of adduction and 10 degrees of internal rotation and also as the maximum possible extension coupled with 10 degrees of external rotation. The effects of prosthetic orientation on activities of daily living were analyzed as well. Results: Acetabular abduction angles of less than 45 degrees decreased flexion and abduction of the hip, whereas higher angles decreased adduction and rotation. Femoral and acetabular anteversion increased flexion but decreased extension. Acetabular abduction angles of between 45 and 55 degrees permitted a better overall range of motion and stability when combined with appropriate acetabular and femoral anteversion. Lower head-neck ratios decreased the range of motion that was possible without prosthetic impingement. The addition of a modular sleeve that increased the diameter of the femoral neck by two millimeters decreased the range of motion by 1.5 to 8.5 degrees, depending on the direction of motion that was studied. Conclusions: There is a complex interplay between the angles of orientation of the femoral and acetabular components. Acetabular abduction angles between 45 and 55 degrees, when combined with appropriate acetabular and femoral anteversion, resulted in a maximum overall range of motion and stability with respect to prosthetic impingement. Clinical Relevance: During total hip arthroplasty, acetabular abduction is often constrained by available bone coverage, while femoral anteversion may be dictated by the geometry of the femoral shaft. For each combination of acetabular abduction and femoral anteversion, there is an optimum range of acetabular anteversion that allows the potential for a maximum range of motion without prosthetic impingement after total hip arthroplasty. These data can be used intraoperatively to determine optimum position.

The femoral component in total hip arthroplasty. Six to eight-year follow-up of one hundred consecutive patients after use of a third-generation cementing technique.

One hundred consecutive patients had a primary unilateral total hip arthroplasty with use of a single design of the femoral component (Harris Precoat), inserted with a so-called third-generation cementing technique, between July 1985 and June 1987. There were seventy-four women and twenty-six men. The mean age at the time of the operation was seventy-one years (range, forty-one to ninety-two years) and the mean weight was seventy kilograms (range, forty-eight to 105 kilograms). Eleven of the 100 patients died during the follow-up period, all with the implant in place. Of the eighty-nine surviving patients, one had a revision arthroplasty for aseptic loosening. The mean duration of clinical follow-up for the remaining eighty-eight patients was seven years (range, six to eight years). The mean Harris hip score at the latest follow-up evaluation was 91 points (range, 68 to 97 points). Of the eighty-eight patients, eighty-five (97 percent) had a good or excellent result. Radiographic follow-up was performed for eighty-one patients; none had evidence of loosening of the stem, and five (6 percent) had endosteal cavitation but were asymptomatic. The rate of failure (loosening or revision) of the femoral component in the entire series was 1 per cent (one hip). The low rate of failure and the maintenance of good and excellent clinical and radiographic results during this period of follow-up are consistent with reports from other institutions. This strengthens the argument to retain or widen the existing indications for the insertion of a femoral stem with cement in primary total hip arthroplasty.

Postoperative surveillance for deep venous thrombosis with duplex ultrasonography after total knee arthroplasty.

Duplex ultrasonography of the lower extremity was used for routine non-invasive screening for asymptomatic proximal and distal deep venous thrombosis, for monitoring of potential propagation of deep venous thrombosis from distal to proximal, and for confirmation of the resolution of proximal deep venous thrombosis after treatment. In the first part of the study, to substantiate the accuracy of duplex ultrasonography, 130 lower limbs (seventy-nine patients) were studied with that modality as well as with venography after a total hip or total knee arthroplasty. Compared with venography, duplex ultrasonography demonstrated 100 per cent sensitivity, specificity, and accuracy for the detection of proximal deep venous thrombosis and 88 per cent sensitivity, 98 per cent specificity, and 98 per cent accuracy for the detection of distal deep venous thrombosis. In the second part of the study, 100 patients who had had a total knee arthroplasty and had been managed with pneumatic stockings and aspirin for prophylaxis against deep venous thrombosis had screening of both lower extremities with duplex ultrasonography on the fourth postoperative day. Duplex ultrasonography demonstrated proximal deep venous thrombosis in seven patients and distal deep venous thrombosis in twenty-two patients; all twenty-nine patients were asymptomatic. The patients who had distal deep venous thrombosis had surveillance with serial duplex ultrasonography on the seventh and fourteenth postoperative days; five of these patients were found to have had propagation of the thrombosis to the proximal deep veins.(ABSTRACT TRUNCATED AT 250 WORDS)

Suboptimal (thin) distal cement mantle thickness as a contributory factor in total hip arthroplasty femoral component failure. A retrospective radiographic analysis favoring distal stem centralization

One hundred cemented total hip arthroplasties (THAs) were evaluated regarding the potential benefit of THA femoral component distal stem centralization, specifically regarding cement mantle thickness. Factors potentially predictive of femoral component mechanical loosening, both relating (22 factors) and not relating (41 factors) to cement, were analyzed on initial postoperative radiographs. Nine THAs with femoral component mechanical failure (group 1) were compared to (1) 88 non-failed THAs (group 2) and (2) 9 matched-paired, nonfailed THAs (group 3). Significant differences were evident regarding minimum and maximum cement mantle thickness in Gruen zone 5 and combined zones 5/6 (groups 1 vs 2 and groups 1 vs 3), with failed femoral components having thinner cement mantles. Discriminate analysis determined minimum cement mantle thickness in zone 5 to be the factor most predictive of femoral component failure. These data indicate that a suboptimal (thin) cement mantle at the medial diaphysis (Gruen zones 5 and 6) contributed to femoral component mechanical loosening in this THA series. This relationship may not pertain to femoral stems of different materials or cross-sectional characteristics. Many THA systems currently provide for a method of centralization of the femoral component distal stem as a mechanism to ensure an adequate circumferential distal cement mantle. Continued investigation into techniques directed toward centralization of the distal femoral stem is warranted by the findings of this study.

Postoperative use of continuous passive motion, transcutaneous electrical nerve stimulation, and continuous cooling pad following total knee arthroplasty*

Three rehabilitation modalities relating to in-hospital postoperative care following unilateral total knee arthroplasty (UTKA) were studied regarding their effect on pain management and UTKA outcome: (1) continuous passive motion (CPM); (2) CPM with transcutaneous electrical nerve stimulation (TENS); and (3) CPM with continuous cooling pad (CCP). Phase I: CPM. Twenty-two UTKA patients were randomized into two postoperative care groups: (1) 12 with CPM; and (2) 10 with no CPM. Total hospitalization pain medication consumption was significantly less for the CPM group (P less than .05). Phase II: CPM With TENS. Forty-eight UTKA patients were randomized into three postoperative care groups: (1) 18 with an ipsilateral thigh TENS unit delivering sensory threshold stimulation; (2) 18 with a subthreshold TENS unit; and (3) 12 with no TENS unit. All groups used CPM. No significant difference was found regarding pain medication consumption. Phase III: CPM With CCP. Thirty consecutive UTKA patients were divided into two postoperative care groups: (1) 15 with a CCP unit; and (2) 15 with no CCP unit. Both groups used CPM. No significant difference was found regarding total or intramuscular hospitalization pain medication consumption. However, oral hospitalization pain medication consumption was significantly less for the CCP group (P less than .01). This postoperative UTKA study demonstrates significantly decreased total in-hospital pain medication consumption when comparing CPM vs no CPM, significantly decreased oral in-hospital pain medication consumption when comparing CPM with CCP vs CPM without CCP, but no difference when comparing CPM with TENS vs CPM without TENS.(ABSTRACT TRUNCATED AT 250 WORDS)

The clinical course of distal deep venous thrombosis after total hip and total knee arthroplasty, as determined with duplex ultrasonography

Duplex ultrasonography was used to screen 273 consecutive patients, on the fourth day after a total hip or total knee arthroplasty, for the presence of a distal deep venous thrombosis. Patients who had a history of thromboembolic disease or who had an active neoplasm were excluded from the study. Of the 273 patients, twenty-four (9 per cent) were found to have a proximal deep venous thrombosis (a thrombosis involving the femoral or popliteal veins) and forty-one (15 per cent), a distal deep venous thrombosis (a thrombosis involving the veins of the calf). All of the thromboses were asymptomatic. The forty-one patients in whom a distal deep venous thrombosis had been detected with duplex screening subsequently had serial duplex examinations, on the seventh and fourteenth postoperative days. If a proximal deep venous thrombosis was detected, anticoagulation was begun immediately. If no proximal thrombosis was observed, the distal thrombosis was considered stable, the serial duplex examinations were terminated, and clinical observation was continued. Of the forty-one patients who had serial examinations, seven (17 per cent) had a proximal deep venous thrombosis in the ipsilateral limb by the fourteenth postoperative day; all seven were asymptomatic, and all were managed with anticoagulation. Thirty-four patients (83 per cent) were determined to have a stable distal deep venous thrombosis on the fourteenth postoperative day, and no additional duplex examinations were performed. Thirty-three (97 per cent) of these thirty-four patients remained asymptomatic for deep venous thrombosis thereafter; the remaining patient (3 per cent) had a proximal deep venous thrombosis in the ipsilateral limb eleven months postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Dissociation of modular hip arthroplasty components after dislocation. A report of three cases at differing dissociation levels.

Modular hip arthroplasty systems, currently widely employed, offer the advantage of increased intraoperative flexibility in component selection with reduced inventory, as well as the disadvantage of modular component dissociation. Dissociation during closed reduction for dislocation is reported in three patients at three different interface levels: (1) fixed acetabular shell-polyethylene linear interface, (2) bipolar acetabular component-femoral head interface, and (3) femoral head-neck interface. Subsequent open reduction was required in each case. Although this potential disadvantage of modular hip systems does not outweigh the benefits, it does warrant that certain precautions be taken when implanting modular components. The acetabular linear should lie flush within the metallic shell after impaction. The femoral head should be firmly impacted onto the neck. Both should resist reasonable manual force of disassembly. Should a modular hip arthroplasty component dislocate, gentle reduction under general anesthesia and fluoroscopic control is warranted. Careful inspection of pre- and postreduction roentgenograms for signs of modular component dissociation is mandatory.

Management of infected total knee arthroplasties.

In a prospective study of 14 consecutive infected total knee arthroplasties ( TKAs ) treated through 1979, the management consisted of: (1) 11 delayed exchange arthroplasties, with 2 failures requiring above-knee amputation; (2) 2 in situ debridements; and (3) 1 arthrodesis. The final outcome of the delayed exchange arthroplasty group regarding joint pain, patient function, and joint performance was (a) inferior to that of primary TKA (before infection), (b) better than that of resection arthroplasty, and (c) worse than that of a control group of non-infected TKAs respectively. Debridement without prosthesis resection was successful only in cases of immediate postoperative infection (2 successes in 4 TKAs ) and uniformly unsuccessful in infections occurring beyond the perioperative period (4 failures in 4 TKAs ). The study indicates that delayed exchange total knee arthroplasty is a reasonable alternative to arthrodesis following resection of an infected TKA and can be performed without undue risk of recurrent infection.

Late deep venous thrombosis and delayed weightbearing after total hip arthroplasty.

One hundred ninety-nine patients who underwent primary total hip arthroplasty and used in hospital pneumatic compression stockings and aspirin as thromboembolic prophylaxis were screened for deep venous thrombosis using duplex ultrasonography on the fourth postoperative day. Of the initial 98 patients, 21 underwent noncemented arthroplasty, maintained touchdown weightbearing for 6 weeks after surgery, and then began progressive partial weightbearing. Of the subsequent 101 patients, 28 underwent noncemented arthroplasty and began progressive weightbearing immediately after surgery. All other patients underwent hybrid arthroplasty and began weightbearing to tolerance immediately after surgery. After duplex screening examination, patients with proximal deep venous thrombosis were given anticoagulation therapy, and patients with negative study results were observed clinically. The relative risk of proximal deep venous thrombosis after noncemented arthroplasty using delayed weightbearing was compared with that after noncemented arthroplasty using immediate progressive weightbearing. Of patients with noncemented arthroplasty, the prevalence of proximal deep venous thrombosis was significantly lower in those using progressive weightbearing immediately after surgery (none) than in those using delayed weightbearing rehabilitation (19%). This study showed that patients undergoing noncemented total hip arthroplasty with delayed weightbearing rehabilitation risk greater potential for deep venous thrombosis after hospital discharge. This study suggests consideration for continued thromboembolic prophylaxis or routine deep venous thrombosis surveillance, or both measures, after hospital discharge, unless more rapid progression of weightbearing is allowed.

Perioperative bladder management after primary total hip arthroplasty

A retrospective review of 95 consecutive primary total hip arthroplasty patients was performed to assess the clinical outcome of two postoperative bladder management protocols. The first 49 patients (group 1) were treated with a pro re nata straight catheterization protocol. The next 46 patients (group 2) were treated with an indwelling catheterization protocol. There were no differences between the groups with respect to sex or age. The patients in group 2 had significantly lower incidences of urinary retention (P < .0005) and bladder distention (P < .0005) than those in group 1. Preoperative systemic diseases and urologic symptoms did not correlate with the occurrence of postoperative urinary retention or bladder distention. There were no infections in group 1. In group 2, one patient (2%) had bacteriuria and one patient (2%) had a urinary tract infection (P > .1). This trend of increased contamination in the catheterization group may be related to a mean catheterization duration of 72 hours.