Radiographic assessment of the thickness lost from polyethylene tibial inserts that had been sterilized differently.

BACKGROUND: Archived serial radiographs of knee replacements provide indirect evidence of the clinical performance of ultra-high molecular weight polyethylene tibial bearings. Our purpose was to determine the loss of thickness in polyethylene tibial inserts that were of the same design but had been sterilized differently. METHODS: Four hundred and sixteen knees with an Anatomic Modular Knee primary total knee replacement had five to eighteen years of follow-up and a posterior cruciate ligament-retaining polyethylene tibial insert that had been sterilized with either gamma radiation in air (from 1987 to 1993) or gamma radiation in an inert gas (from 1993 to 1995), or by means of a nonirradiation gas-plasma method (from 1995 to 2001). Readings were taken from 1975 weight-bearing anteroposterior radiographs of the knee on which the top surface of the metal tibial tray had nearly projected as a line. In each tibiofemoral compartment, loss of polyethylene thickness was calculated as the standard thickness of the insert minus the measured magnification-corrected thickness. For each sterilization method, thickness loss was plotted versus the corresponding follow-up time, and a mixed linear regression model was used to quantify the change in thickness over time. Multiple linear regression analysis was used to determine whether loss of thickness was associated with implant factors, patient variables, and early postoperative limb alignment. RESULTS: According to the mixed model regression coefficients, loss of medial compartment thickness was greatest for inserts that had been sterilized with gamma radiation in air (0.15 mm/yr), least for those sterilized with gamma radiation in an inert gas (0.02 mm/yr), and of an intermediate magnitude for those sterilized with a nonirradiation method (0.06 mm/year); loss of lateral compartment thickness ranged from 0.03 to 0.06 mm/yr. Notably, no insert irradiated in an inert gas showed a loss of thickness of >1 mm, and no nonirradiated insert showed a loss of >2 mm. Loss of medial compartment thickness in inserts sterilized with radiation in air increased significantly with a greater polyethylene shelf age, lesser patient age, and more varus alignment of the limb in the early postoperative period (p < 0.01). CONCLUSIONS: In this total knee design, tibial polyethylene performance improved markedly after discontinuation of the gamma radiation in air sterilization technique. Future concerns are that bearings sterilized with radiation in an inert gas may oxidize in vivo and develop fatigue wear because of free radicals generated during sterilization with radiation and that nonirradiated bearings may undergo greater losses in thickness from routine burnishing since they lack the cross-linking that accompanies sterilization with radiation.

Video-assisted thoracoscopic surgery using single-lumen endotracheal tube anesthesia.

BACKGROUND: Most general thoracic surgeons use double-lumen endotracheal tube (DLET) anesthesia for all video-assisted thoracoscopic surgery (VATS). We evaluated a single-lumen endotracheal tube (SLET) for VATS for drainage of pleural effusions and pleural biopsies. METHODS: A consecutive series of patients with recurrent pleural effusions underwent VATS using an SLET and only one incision. Operations were accomplished via one 2-cm incision using a 5-mm rigid thoracoscope and mediastinoscopic biopsy forceps for directed pleural biopsies. A working area was accomplished with low tidal volumes. RESULTS: There were 376 patients (191 women). The indications for VATS were a nondiagnosed or benign pleural effusion in 294 patients, and a malignant effusion in 82 patients. Two hundred eight patients underwent biopsy of the parietal pleura, and mean operative time was 17 min. Adequate visibility was obtained in all. When compared to preoperative cytology, VATS was more sensitive (45% compared to 99%, p < 0.001), had a higher negative predictive value (56% compared to 99%, p < 0.001), and was more accurate (67% compared to 99%, p < 0.001). Forty-seven percent of patients with a history of cancer had false-negative preoperative cytology results. Complications occurred in seven patients (2%), and there were three operative deaths (none related to the operative procedure). CONCLUSION: VATS using SLET and only one incision is possible, and it affords excellent visualization of the pleural space, allowing pleural biopsies and talc insufflation. It avoids the risk, time, and cost of a DLET. It is significantly more sensitive and accurate than preoperative cytology, and it should be considered as the diagnostic and therapeutic procedure of choice in patients with recurrent pleural effusions.

Vascular injuries in knee dislocations: the role of physical examination in determining the need for arteriography.

BACKGROUND: Popliteal artery injury is frequently associated with knee dislocation following blunt trauma, an injury that is being seen with increasing frequency. The primary purpose of the present study was to evaluate the use of physical examination to determine the need for arteriography in a large series of patients with knee dislocation. The secondary purpose was to evaluate the correlation between physical examination findings and clinically important vascular injury in the subgroup of patients who underwent arteriography. METHODS: One hundred and thirty consecutive patients (138 knees) who had sustained an acute multiligamentous knee injury were evaluated at our level-1 trauma center between August 1996 and May 2002 and were included in a prospective outcome study. Four patients (four knees) were lost to follow-up, leaving 126 patients (134 knees) available for inclusion in the study. The results of the physical examination of the vascular status of the extremities were used to determine the need for arteriography. The mean duration of follow-up was nineteen months (range, eight to forty-eight months). Physical examination findings, magnetic resonance imaging findings, and surgical findings were combined to determine the extent of ligamentous damage. RESULTS: Nine patients had flow-limiting popliteal artery damage, for an overall prevalence of 7%. Ten patients had abnormal findings on physical examination, with one patient having a false-positive result and nine having a true-positive result. The knee dislocations in the nine patients with popliteal artery damage were classified, according to the Wascher modification of the Schenck system, as KD-III (one knee), KD-IV (seven knees), and KD-V (one knee). CONCLUSIONS: Selective arteriography based on serial physical examinations is a safe and prudent policy following knee dislocation. There is a strong correlation between the results of physical examination and the need for arteriography. Increased vigilance may be justified in the case of a patient with a KD-IV dislocation, for whom serial examinations should continue for at least forty-eight hours.

Use of a hinged external knee fixator after surgery for knee dislocation.

PURPOSE: This study documents short-term clinical outcomes in patients with knee dislocations after blunt trauma and evaluates the compass knee hinge (CKH) external fixator for their treatment. TYPE OF STUDY: Nonrandomized prospective functional outcome study. METHODS: Forty patients with 43 knee dislocations were evaluated. Twelve knees underwent ligament reconstruction followed by placement of a CKH; this was group A. Group B included 27 knees that underwent the same treatment and rehabilitation protocol except that an external brace was used rather than a CKH. RESULTS: Thirty-six patients with 39 knee dislocations underwent follow-up ranging from 14 to 41 months (mean, 24). Four patients with 4 knee dislocations were lost to follow-up (1 group A, 3 group B). Group A underwent 27 knee ligament procedures with 2 (7%) failures based on clinical examination. Group B underwent 102 ligament procedures with 30 (29%) failures (P <.05). Anterior cruciate ligament (ACL) reconstruction revealed that 7 group A patients experienced 1 (14%) failure and 25 Group B patients experienced 7 (28%) failures. Posterior cruciate ligament (PCL) reconstruction in 7 group A patients included no failures, and 20 PCL reconstructions in group B included 1 failure. Reconstruction of the posterolateral corner (PLC) yielded no failures in 2 group A patients and 5 (25%) of 20 in group B. Repair of 8 PLCs in group A yielded 1 (12.5%) failure and 26 PLC repairs in group B had 14 (54%; P =.05). SF-36 data revealed low mean values with no significant differences between groups with current enrollment. CONCLUSIONS: Knee dislocation after blunt trauma requires aggressive surgical treatment and physical therapy. In the short-term evaluation, the CKH allows aggressive physical therapy without placing repaired or reconstructed ligaments under high stresses that can result in failure.

Anatomic reconstruction of the posterior cruciate ligament after multiligament knee injuries. A combination of the tibial-inlay and two-femoral-tunnel techniques.

BACKGROUND: Neither operative nor nonoperative treatment of posterior cruciate ligament rupture after multiligament knee injuries have shown very favorable outcomes. HYPOTHESIS: Reconstruction of the posterior cruciate ligament by combining the tibial-inlay and two-femoral-tunnel techniques will result in improved stability and functional outcomes. STUDY DESIGN: Prospective cohort study. METHODS: Twenty-nine patients with 30 posterior cruciate ligament ruptures and multiligament knee injuries treated with the combined technique were evaluated with clinical, radiographic, and functional outcome measures. RESULTS: All patients had a clinical examination result indicating joint stability (0 or 1+) at an average follow-up of 25 months (range, 15 to 39). Twenty-three knees had no laxity, and seven had 1+ laxity. The KT-2000 arthrometer data documented less than 0.5 mm of side-to-side mean difference for both posterior displacement and total anterior-posterior displacement at both 30 degrees and 70 degrees of knee flexion. Knee range of motion was a mean extension of 1 degrees (range, 0 degrees to 10 degrees ) and a mean flexion of 124 degrees (range, 75 degrees to 145 degrees ). Mean Lysholm knee score was 89.4. CONCLUSIONS: Reconstruction with a combination tibial-inlay and two-femoral-tunnel technique provides good results after multiligament knee injuries. All patients had a stable posterior cruciate ligament at most recent clinical follow-up, and 77% had no laxity at all.

Heterotopic ossification associated with knee dislocation.

PURPOSE: The purpose of this study was to determine the prevalence of heterotopic ossification following knee dislocation. TYPE OF STUDY: Prospective clinical evaluation and a retrospective chart review. METHODS: This study evaluated 57 knees in 55 patients who sustained high-energy blunt trauma with resultant knee dislocations. Radiographs were reviewed by 2 of the authors (J.P.S., T.C.W.), and the incidence of heterotopic ossification (HO) was documented. Additionally, patients were classified regarding the degree of HO on a scale from 0 to 4. One is punctate calcification, 2 is HO involving less than 50% of the joint space; 3 is HO involving more than 50%; and 4 is ankylosis of the joint. RESULTS: Thirteen patients with 15 knee dislocations developed HO. The incidence of HO was 26%. Seven knees demonstrated severe HO (grade 3 or 4) which represented an incidence of 12% of all knee dislocations. Injury severity score for both groups was 18, documenting that the patients in this study represent multiple trauma patients. There was no significant difference in the incidence of HO based on mechanism of injury with the current number enrolled in the study. However, 60% (3 of 5) of patients involved in a motor vehicle versus pedestrian accident developed HO. There was a significant increase in the incidence of arthrofibrosis in patients with severe HO (P <.05). Patients with significant HO had a mean flexion of 97 degrees, compared with flexion of 117 degrees in patients with no or mild HO. This difference was borderline significant (P =.058). There was no difference between the groups in mean extension. There was a significant increase in knee HO in patients with HO at another anatomic site (P =.01). CONCLUSIONS: HO is a common problem following knee dislocation. Of the 7 knees with severe HO, 5 developed HO medially, 4 developed HO posteriorly, 3 developed HO laterally, and only 1 had involvement anteriorly. A similar distribution was present in the patients with mild HO, with posterior and medial ossification being the most common. Five of the 7 severe HO cases involved at least 3 of the 4 sides (anterior, posterior, medial, or lateral) of the knee. Patients were evaluated for the presence of head injury and any relationship to the development of HO around the knee. There was no increased incidence of HO around the knee in our 10 patients with severe head injuries when compared with those with no head injury. There was also no increased incidence of HO in knee dislocations associated with periarticular fractures.