Rudolf Schabus

The diagnosis of meniscal tears in athletes : A comparison of clinical and magnetic resonance imaging investigations

This study evaluated the predictability of clinical examination alone in comparison with magnetic resonance imaging in the diagnosis of meniscal tears in competitive athletes. Ninety-three competitive athletes were prospectively investigated between 1992 and 1995. A total of 57 athletes were operated on based on clinical examination alone, and the 36 remaining athletes had magnetic resonance imaging before surgery. The correct diagnosis of a meniscal lesion was made on clinical examination alone in 83 athletes (89%) and on magnetic resonance imaging the correct diagnosis was also made in 89% of 36 athletes. The overall values for the clinical investigation of the medial and lateral menisci combined were 94.5%, 91.5%, 99%, 96.5%, 87% for accuracy, positive predictive value, negative predictive value, sensitivity, and specificity, respectively. The overall values for magnetic resonance imaging of the medial and lateral menisci combined were 95.5%, 96.5%, 91.5%, 98%, 85.5% for accuracy, positive predictive value, negative predictive value, sensitivity, and specificity, respectively.This study evaluated the predictability of clinical exam ination alone in comparison with magnetic resonance imaging in the diagnosis of meniscal tears in compet itive athletes. Ninety-three competitive athletes were prospectively investigated between 1992 and 1995. A total of 57 athletes were operated on based on clinical examination alone, and the 36 remaining athletes had magnetic resonance imaging before surgery. The cor rect diagnosis of a meniscal lesion was made on clin ical examination alone in 83 athletes (89%) and on magnetic resonance imaging the correct diagnosis was also made in 89% of 36 athletes. The overall values for the clinical investigation of the medial and lateral me nisci combined were 94.5%, 91.5%, 99%, 96.5%, 87% for accuracy, positive predictive value, negative predic tive value, sensitivity, and specificity, respectively. The overall values for magnetic resonance imaging of the medial and lateral menisci combined were 95.5%, 96.5%, 91.5%, 98%, 85.5% for accuracy, positive pre dictive value, negative predictive value, sensitivity, and specificity, respectively.

Shortening of the Patellar Tendon After Anterior Cruciate Ligament Reconstruction

In this prospective study, patellar height changes were investigated after anterior cruciate ligament (ACL) reconstruction with a mean follow-up of 22.4 months. A total of 114 patients were included. Fifty-two patients (group A) were treated by multiple suture repair, 27 patients (group B) underwent acute ACL reconstruction, and 35 patients (group C) underwent ACL reconstruction > or =6 weeks after injury with a patellar tendon graft. The patellar vertical height ratios (VHR) were evaluated preoperatively (VHR 1), 6 months postoperatively (VHR 2), and at follow-up (VHR 3). For the studied questions, the following answers were obtained: (1) The change of the patella height was the same in all three groups (i.e., disregarding the different surgical procedures). (2) The time elapsed between injury and ACL reconstruction did not influence the shortening of the patellar tendon. (3) Women showed a more pronounced shortening of the patellar tendon than did men. (4) A significant shortening of the patellar tendon occurred in 30% of our patients, and the process of shortening was finished 6 months postoperatively. (5) Anterior knee pain was present in 27.2% of our patients and occurred significantly more often after patellar tendon graftings. (6) Age had no influence on the changes of the patellar height.

Cyclops and cyclopoid formation after anterior cruciate ligament reconstruction: clinical and histomorphological differences

Abstract Prospectively, 119 patients were pursued clinically and by follow-up-arthroscopy for the occurrence of a “cyclops syndrome” after ACL reconstruction with a patellar tendon autograft, augmented by LAD. Twenty-one patients showed nodular formations. Ten of these (group 1) developed early clinical evidence of a “cyclops syndrome” with a mean extension deficit of 19° before follow-up-arthroscopy, on average 5.9 months after the index operation. The nodular formations found and excised during débridement had a hard consistency. Histomorphological undecalcified microtome section evaluation of six specimens revealed fibrocartilagineous tissue with active bone formation in the center. The other 11 patients showed no clinical symptoms (group 2). A similar but soft nodulous scar formation was detected at follow-up-arthroscopy, on average 9.5 months after the index operation. Histomorphologically these so-called “cyclopoid” formations were only built-up fibrocartilagineous islands surrounded by granulation tissue. Neither remnants of tendon graft fibers nor old bone particles were found in specimens of either group. It can be concluded that both the hard cyclops and the soft “cyclopoid” are de novo scar formations.

Patellar alignment evaluated by MRI

We analyzed the congruence of the articular cartilage surfaces and the corresponding subchondral bone in the patellar joint. 20 volunteers underwent MRI investigations of the right patellar joint in 20 degree and 45 degree flexion in the axial plane. The sulcus, congruence, and lateral patellofemoral angles, measured on MRI slices centered through the midtransverse patella, were recorded. In 20 degree and 45 degree knee flexion, the bony sulcus and lateral patellofemoral angles were significantly different from the respective cartilagineous angle. We conclude that 1) measurement of the bony sulcus and lateral patellofemoral angles does not allow conclusions about the articular cartilage surface and its thickness, 2) the bony congruence angle corresponds well to the articular cartilage surface as an indicator of patellar centralization.

Synthetic augmented repair of proximal ruptures of the anterior cruciate ligament. Long-term results of 66 patients.

The long-term results (five-to eight-year follow-up evaluation) of 66 patients with high proximal ruptures of the anterior cruciate ligament (ACL) who were treated operatively are presented in a retrospective and uncontrolled study. Technique of surgery was the reinsertion of the ACL in a multiple suture loop technique, augmented with Kennedy-LAD (ligament augmentation device) on over the top route in temporary double-end fixation. This technique was used in patients with proximal rupture of the anterior cruciate ligament found at arthroscopy. In the follow-up as well as in instrumented measurement, 97% of the knee joints have normal joint laxity. According to the evaluation sheet designed by the Orthopädische Arbeitsgemeinschaft Knie (OAK), excellent or good results were found in 86% of the patients. Nine percent had limited range of motion. The ACL reconstruction technique allowed 75% of the patients to regain their preinjury sports activity level. The potential advantages of synthetic augmented reinsertion of the ACL are anatomic reconstruction without destruction of other anatomic structures as grafts; securing early rehabilitation with weight bearing of the operated limb depending on individual pain tolerance; and presenting excellent long-term results of normal joint laxity.

Light and electron microscopic study of stress-shielding effects on rat patellar tendon.

Abstract In this second part of our study, the histomorphologic changes occurring in the patellar tendon (PT) of rats after sole stress-shielding were evaluated. In seven adult albino rats, both PTs were exposed by straight skin incision and then stress-shielded on one side by a cerclage, while the contralateral PT served as the sham-operated control. One animal died after the operation and was used as a negative control. After 10 weeks of otherwise unrestricted motion, the rats were killed, and the histomorphology of all PT specimen pairs compared by light and transmission electron microscopy. Light microscopy showed mid-portion thickening and irregularity of collagen bundles in the stress-shielded tendons. Intense remodelling was demonstrated by increased cellularity and vascularity, as well as by enrichment in acidic proteoglycans. Ultrastructural evaluation and morphometry revealed a predominance of large diameter (peak between 180 and 260 nm) collagen fibrils in the sham-operated controls, while in the stress-shielded tendons the number of apparently new, small-diameter (peak between 40 and 60 nm) collagen fibrils increased (up to 77% per cross-sectional field of view). The difference in peak diameters was statistically significant (p < 0.0005). This rat model demonstrated that sole stress-shielding not only causes biomechanical alterations, but also intense tissue remodelling and significant morphological changes in the collagen fibrils in the patellar tendon, comparable to so-called ‘ligamentization’ in experimental and clinical patellar tendon grafts for anterior cruciate ligament reconstruction.

Twisting of patellar tendon grafts does not reduce their mechanical properties

The purpose of this study was to investigate whether the twisting of a patellar tendon (PT) graft improves or reduces its mechanical properties. Twenty-seven pairs of 10 mm cadaveric PT grafts were tested at a strain rate of 10% min(-1). For each pair, the left specimen served as an unmanipulated control while the right specimen was either left untwisted, twisted + 90 degrees, or twisted - 90 degrees. All avulsion failures were excluded from the data analysis, focusing only on pure in-substance tendon ruptures. Higher ultimate load values than previously reported were obtained for both the twisted and untwisted specimens, without a statistical significant difference between the two. The values obtained for the left and right specimens from Group A were 4014+/-319 and 3973+/-245 N, from Group B 3613+/-207 and 3891+/-14 N, and from Group C 3997+/-278 and 4415+/-507 N, respectively. Stiffness and failure strain were not influenced by the twisting. Neither the presence of a twist, nor the direction of the twist were found to increase the ultimate load of the 10 mm cadaveric patellar tendon graft. Therefore, recommendation for twisting cannot be assessed to its mechanical properties.

Measurement of stress-strain relationship and stress relaxation in various synthetic ligaments.

In an experimental study various synthetic augmentation devices for knee ligament surgery were tested in a servo-mechanical universal tensile testing machine under uniaxial loading. Two tests were done to elucidate the mechanical behaviour: stress relaxation and stress-strain relationship. Regarding the point of failure or rupture, the strongest ligament was the Trevira et 1800 N, followed by the 8-mm-wide Kennedy LAD at 1720 N. At a working load of 500 N the Gore-tex band, the Trevira, and the Kennedy-LAD stretched by between 2% and 3%. For synthetic augmentation in repair of proximally ruptured anterior cruciate ligaments we recommend a synthetic ligament that reaches failure point at a load of more than 1000 N with an alteration in length of less than 5%. Otherwise, stress protection of the biological reconstruction in full extension will be impossible. The requisite criteria were fulfilled by the Trevira, Kennedy-LAD and Gore-tex synthetic ligaments.

Mechanical properties of a rat patellar tendon stress-shielded in situ.

Abstract The effects of stress deprivation on the mechanical properties of the patellar tendon (PT) were studied using 14 albino rats. The PT was stress-shielded with cerclages on one side, while the contralateral patellar tendon served as a sham-operated control. After 10 weeks, paired load-strain as well as load-relaxation experiments were performed (11 and 3 specimen pairs, respectively). Mechanical tests showed, irrespective of the cerclage material used, that strain was increased significantly after stress-shielding (P < 0.02). The time constant significantly decreased in the stress-shielded specimens under ¶5 N loads, which may be considered ‘physiological’. Tissue remodeling might explain the observed changes in the viscoelastic behaviour of the stress-shielded tendons. Loading, even in the physiological range of normal daily activity, may lead to an elongation of previously stress-shielded tendons or ligaments and consequently alter the behaviour of a joint.

Epidermoid cyst after arthroscopic knee surgery

Eleven years after an arthroscopic procedure, a benign tumor of the knee located beneath the scar where the outflow canula was placed was excised. Histomorphological evaluation determined the diagnosis of an epidermoid cyst. This is the first case reported in the literature of an epidermoid cyst occurring after an arthroscopic operation. The previous epidermoid cysts reported were found after trauma or after dermal grafting for epithelium implantation.