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International Journal of Anatomical Sciences 2010, 1: 26-30

 Research Paper

 Morphology of the Intercondylar Notch and its Clinical Significance

 Ravichandran D,a Melani R.b

 Department of Anatomy, VMKV Medical College, Salem, Tamil Nadu, India; bDepartment of

Anatomy, SRMC &RI, Sri Ramachandra University, Chennai, Tamil Nadu, India.

 Key Words: intercondylar notch, dimensions, anterior cruciate ligament

 Abstract: The dimensions of the intercondylar notch of dry femora and in cadavers were  measured  and  their  clinical  implications  were  assessed.    The  study  was conducted in two groups, Group A (dry bones) and Group B (cadaveric knees). The dimensions including notch width, condylar width,  notch depth, condylar depth and the shape of the notch were measured using standard guidelines in both groups.  In group  B,  the status  of  the anterior  cruciate ligament  (ACL)  was  also  noted and categorized. Using these datas, the notch width index (NWI) and notch depth index (NDI) were calculated. The results were analyzed statistically. The average notch width index was found to be 0.252 in dry bones and 0.230 in cadavers. The average notch depth index was found to be 0.467 in dry bones and 0.502 in cadavers. The shape of the notch (in both groups) in majority of the cases was “inverted U” and in few cases it was “triangular”. Sixteen knees showed laxity of ACL with marginal reduction of both indices. The clinical implications are discussed.

 The shape of the intercondylar notch plays an important role in knee injuries. Triangular   shaped   notches   with   straight edges cause damage to the ligaments. The shape of the intercondylar notches were observed by many investigators (Anderson et al., 1987; Souryal and Freeman, 1993 and Shickendantz and Weiker 1993).    The morphology of  the  intercondylar  notch  of the femur is related to the functioning of the cruciate ligaments.   Abnormally narrow (stenotic) notches have been shown to increase the incidence of anterior cruciate ligament (ACL) injuries. The lower end of the femur presents two rounded and eccentrically curved condyles.   The groove present anteriorly between them is called the patello-femoral groove.     The notch separating them posteriorly is the intercondylar    notch    (Williams    et    al.,1995).The cruciate ligaments have intimate embryological and functional relationship to the   intercondylar   notch   (Robert   Miller,2008).  The space available for the cruciate ligament is determined by the dimensions of the notch including the depth, width and shape.

Correspondance to: Ravichandran D, Department of  Anatomy, VMKV Medical College, Salem 636 007

Tamil Nadu, India

Email: [email protected]

Narrowing of the intercondylar notch is termed as “intercondylar notch stenosis”. Few authors have noted a strong association between stenotic intercondylar notches and anterior cruciate ligament injuries (Souryal and Freeman 1993). The intercondylar notch is found to be significantly smaller in knees with severe osteoarthritis due to osteophyte growth in the notch (Wada et al., 1999), thus increasing the incidence of ACL ruptures in patients  with  degenerative  arthritis (Heriberto Ojeda Leon et al.,    2005). Literature regarding the morphology of the intercondylar notch in Indian population is  scarce. Therefore an attempt has been made to determine these dimensions and their clinical implications in Indian population.

 Materials and Methods

The study was conducted in two groups (A & B).  Group A comprised of dry bone samples (n= 200 femora) and group B, cadaveric knees (n=40).   Dry bones and cadaveric knees from the Departments of Anatomy, Vinayaka Missions Kirupananda Variyar Medical College, Salem and Sri Ramachandra Medical College & Research Institute, Sri Ramachandra University, Chennai were utilized for this study.

i)  The dimensions of the femoral condyles and intercondylar notches were measured using  a  vernier  caliper.    In  group A,  the measurements were taken directly from the bones and in group B, the measurements were taken in the cadavers at the anterior outlet  of  the  knees  with  the  knee  in  90 degrees flexion (Fig.1).

 The measurements of the parameters were taken according to the guidelines given by Anderson  et  al.,  1987;  Herzog  et  al.,1994 and Wada et al., 1999. In both the groups,  the  notch  width  represented  the width of the notch at two-thirds of the notch depth. The notch depth was identified as the maximum height of the intercondylar notch. The width of the femoral condyle between both epicondyles was measured as the condylar width and the maximum antero- posterior height of the lateral femoral condyle was measured (Wada et al., 1992) as the condylar depth (Fig. 2).   The notch width index (NWI) and notch depth index (NDI) were calculated with these data. The shape of the intercondylar notches and the status of the ACL were also studied. The results were tabulated and analyzed statistically. The data of this study was analyzed using SPSS 15.0.

 The Descriptive Statistics like N, percentage, range, mean & standard error of mean including the Inferential statistics like student’s t-test (Swan, 2005) with p – value of dry bone parameters and cadaver parameters  are  tabulated  (Table  1).  The mean + SE of NWI and NDI in group A was found to be 0.252 + 0.002 and 0.467 + 0.003 respectively.  The  mean  NWI  and  NDI  ingroup  B  was  0.231  +  0.003  and  0.503  + 0.013 respectively.

 The shape of the notch in 67% of group A and 80% of group B was found to be “inverted U” and 33% of group A and 20% of group B showed triangular shaped notches  (Fig.  3).  16  knees  in  group  B showed  laxity  of ACL and  24  knees  had normal  ACL.  A comparison  of  NWI  and NDI between the knees with normal ACL and lax ACL showed a marginal reduction of both the indices in the knees with laxity  of ACL ( 0.227  and 0.514 respectively).

Table 1. Descriptive & inferential statistics

Fig. 3 Different shapes of the intercondylar notch noted in the present study

Fig.4 Shows lax ACL in one of the knees of   Group B

Discussion

 The ACL is  one  of  the  commonly injured ligaments in athletes and in patients with  degenerative  osteoarthritis. Orthopaedic surgeons describe the injuries of ACL as “the beginning of the end of the knee”.    The exact incidence remains unknown (Robert Miller, 2008).   The ACL courses approximately at an angle of 40 degrees from its tibial attachment to the femoral attachment.    The roof of the intercondylar notch is inclined 40 degrees to the longitudinal axis of the femur so that when the knee is in full extension, the roof is near the anterior surface of the anterior cruciate  ligament  (Robert  Miller,  2008). The  morphology  of  the  notch  therefore plays a very important role in the injuries of ACL.

 In this regard, notch width index (NWI) has frequently been used as an indicator of stenosis (NWI < 0.20) of the intercondylar notch (Anderson et al., 1987; Souryal and Freeman 1993; Shickendantz and Weiker, 1993). The NWI represents the ratio  of  the  notch  width  to  the  condylar width of the femur. In his study on 902 high school  athletes  using  tunnel  view radiographs of the knee joint, Souryal and Freeman (1993) found the normal notch width index to be 0.231 + 0.044. In the present  study  a  comparison  of  NWI  and NDI between knees with normal ACL and  lax ACL in group B, a marginal reduction of both  the  indices  were  noted  in  the  knees with laxity of ACL. This difference was not found  to  be  statistically  significant  (p= 0.605   and   0.804   respectively).   Yet   it indicates a mild degree stenosis and hence a dysfunctional (lax) ACL.   Therefore this study is more in favour of the association between   the   notch   stenosis   and   ACL damage   and   feel   that   critical   stenotic notches   (NWI<0.20)   may   predispose   to ACL tears.

 Souryal and Freeman (1993) also observed variations of the index between men and women. The index for males was found to be larger than women.   Therefore the female population is at a higher risk for ACL injuries than men.

Notch depth index (NDI) has also been used by some authors to predict the stenosis of the intercondylar notch (Wada et al., 1999), who had calculated the NDI as a ratio of the notch depth to condylar depth.

 Anderson et al., 1987 observed variations in the shape of the intercondylar notch. According to him the shape may be “inverted U”, triangular or wave shaped. A narrow, triangular notch with straight edges increases the incidence of ACL ruptures (Shepstone 2001). The results of the present study in terms of NWI and NDI vary marginally with the observations of other authors. The NWI in the present study in group A (0.252 + 0.002) is observed to be slightly higher than the average value (0.231 + 0.044) as observed by Souryal and Freeman, 1993.   The NWI as observed in group B in the present study is same as that observed by  Souryal and Freeman, 1993 (ie 0.231). The NDI in the present study in group A (0.467  + 0.003) and  in  group  B (0.503 + 0.013) is almost similar to the observations of Wada et al.,(1999).

 Controversy exists among different authors regarding the association between intercondylar   notch   stenosis   and   ACL injuries. Muneta et al., (1997) and Teitz et al., (1997) have proved that intercondyar notch stenosis is not a significant risk factor for ACL tears. However a strong association between the intercondylar notch stensois in degenerative arthritis of the knee and increased  incidence  of  ACL  damage  has been  confirmed  by  others  (Wada  et  al., 1999; Heriberto Ojeda Leon et al., 2005).